Field of the Art
The present invention relates to a keyboard assembly for providing electrical outputs corresponding to multiple keys, to signal utilization of the keys of electronic devices such as typewriters and other data processing equipment.
In such a keyboard for electronic devices, a large number of keys are disposed in plural rows to provide electronic signals corresponding to the keys which have been operated on their top faces. For increased ease of operation and identification of the keys, and for reduced fatigue of the operator, an operating surface generally defined by the top faces of the individual keys is curved to a downwardly convex shape in a plane perpendicular to the rows of the keys.
To obtain such a curved operating surface of keys, a known keyboard is constructed as illustrated in FIG. 11, wherein multiple keystem guides 101 are formed as integral parts of an upper casing 100 of the keyboard. The keystem guides 101 are formed so as to slidably support corresponding keystems 102 which carry at their upper ends respective keytops 103. The keystems 102 of the keys are formed with different lengths, and the keytops 103 are given different shapes, depending upon the rows in which the keys are disposed, whereby an operating surface defined by the curved top faces of the keytops 103 is downwardly curved.
Another arrangement for establishing a downward curvature of the operating surface of the keytops is shown in FIGS. 12(A) and 12(B), which arrangement is disclosed in U.S. patent application Ser. No. 624,395 filed June 25, 1984 (and issued as U.S. Pat. No. 4,560,844 on Dec. 24, 1985), assigned in part to the assignee of the present application, and claiming the benefit of the filing dates of Japanese patent application No. 58-125740, No. 58-127529 and No. 58-127530, filed July 11, 1983, Aug. 17, 1983 and Aug. 17, 1983, respectively, which were laid open after the filing date of Japanese Patent Application No. 59-185201 the benefit of which is claimed in the present application. In this arrangement, a key-holder plate 112 has a multiplicity of keystem guides 111 for guiding keystems 115. This key-holder plate 112 is molded together with an upper casing 110 so that the key-holder plate 112 is connected, only at its limited peripheral positions, to an upper casing 110 of the keyboard. A curved retainer metal plate 113 is disposed in order to hold the otherwise flat key-holder plate 112 in a downwardly curved posture so that an operating surface 117 of keytops 116 is downwardly curved following the curvature of the retainer metal plate 113.